Personal experience:
First of all, try to choose some brands if you can. After all, brands are relatively more reliable, such as Shuangyang, Yipin Wang, Huchen Zhou, Populus euphratica and Santu, which are well-known brands in China. Specifically, whether the brush is good or not is traditionally four words: sharp, round, neat and healthy. A tip refers to a pen that has been opened. After the pen is dipped in ink, the tip of the pen must be sharp. If there are more water chestnuts, it is not a good pen. Round, refers to the pen belly, to be full and round; Because of the quality problem, there are bumps on the pen. Qi refers to the pen that has been opened. After drying, hold the nib with two fingers, and the nib is in a straight line. If there are sharp edges of different lengths, it is unqualified. Health means that written writing should have "certain" flexibility; Press writing, lift the pen, and the nib will automatically recover. The better the resilience, the better the flexibility of the pen (note that a pen with good flexibility is not necessarily a good pen, and vice versa).
Sharp, round, neat and healthy are just the basic requirements for choosing a writing brush. A really good pen needs to be read, touched and tried with the nib open to dry. Look at the transparency of the pen in the light. Feng Ying's high transparency shows that the written materials are good, otherwise it is likely to be made of velvet. Touch, gently hold the brush hair with two fingers and slide, feeling soft and comfortable, indicating that the material is good, otherwise it is not good. Try it. It's simple. Dip in ink and lick the pen and write it yourself. Mainly depends on the ink storage and the effect of sealing the front; Generally speaking, the softer the pen, the more ink it stores, which is suitable for writing lines and grass. The harder the pen is, the less ink is stored, which is suitable for drawing or writing letters.
Brush is the most important tool for learning calligraphy. Of course, choosing a pen is only the first step. To really practice calligraphy well, you still need correct methods and efforts.